scholarly journals Surface flux estimates derived from UAS-based mole fraction measurements by means of a nocturnal boundary layer budget approach

2019 ◽  
Author(s):  
Martin Kunz ◽  
Jost V. Lavric ◽  
Rainer Gasche ◽  
Christoph Gerbig ◽  
Richard H. Grant ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Mole Fraction ◽  
Surface Flux ◽  
Nocturnal Boundary Layer ◽  
Carbon Dioxide Flux ◽  
Unmanned Aircraft ◽  
Atmospheric Conditions ◽  
Transport Modelling ◽  
Stable Conditions

Abstract. The carbon exchange between ecosystems and the atmosphere has a large influence on the Earth system and specifically on the climate. This exchange is therefore being studied intensively, often using the eddy covariance (EC) technique. EC measurements provide reliable results under turbulent atmospheric conditions, but under stable conditions – as they often occur at night – these measurements are known to misrepresent exchange fluxes. Nocturnal boundary layer (NBL) budgets can provide independent flux estimates under stable conditions, but their application so far has been limited by rather high cost and practical difficulties. Unmanned aircraft systems (UASs) equipped with trace gas analysers have the potential to make this method more accessible. We present the methodology and results of a proof of concept study carried out during the ScaleX 2016 campaign. Successive vertical profiles of carbon dioxide dry air mole fraction in the NBL were taken with a compact analyser carried by a UAS. We estimate an average carbon dioxide flux of 12 μmol m−2 s−1, which is plausible for nocturnal respiration in this region in summer. Transport modelling suggests that the NBL budgets represent an area on the order of 100 km2.

scholarly journals Surface flux estimates derived from UAS-based mole fraction measurements by means of a nocturnal boundary layer budget approach

2020 ◽  
Vol 13 (4) ◽  
pp. 1671-1692 ◽  
Author(s):  
Martin Kunz ◽  
Jost V. Lavric ◽  
Rainer Gasche ◽  
Christoph Gerbig ◽  
Richard H. Grant ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Mole Fraction ◽  
Surface Flux ◽  
Nocturnal Boundary Layer ◽  
Carbon Dioxide Flux ◽  
Unmanned Aircraft ◽  
Atmospheric Conditions ◽  
Transport Modelling ◽  
Stable Conditions

Abstract. The carbon exchange between ecosystems and the atmosphere has a large influence on the Earth system and specifically on the climate. This exchange is therefore being studied intensively, often using the eddy covariance (EC) technique. EC measurements provide reliable results under turbulent atmospheric conditions, but under calm and stable conditions – as they often occur at night – these measurements are known to misrepresent exchange fluxes. Nocturnal boundary layer (NBL) budgets can provide independent flux estimates under stable conditions, but their application so far has been limited by rather high cost and practical difficulties. Unmanned aircraft systems (UASs) equipped with trace gas analysers have the potential to make this method more accessible. We present the methodology and results of a proof-of-concept study carried out during the ScaleX 2016 campaign. Successive vertical profiles of carbon dioxide dry-air mole fraction in the NBL were taken with a compact analyser carried by a UAS. We estimate an average carbon dioxide flux of 12 µmolm-2s-1, which is plausible for nocturnal respiration in this region in summer. Transport modelling suggests that the NBL budgets represent an area on the order of 100 km2.

scholarly journals Carbon dioxide measurements in the nocturnal boundary layer over Amazonian forest

1999 ◽  
Vol 3 (1) ◽  
pp. 39-53 ◽  
Author(s):  
A. D. Culf ◽  
G. Fisch ◽  
Y. Malhi ◽  
R. Carvalho Costa ◽  
A. D. Nobre ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Carbon Dioxide Concentration ◽  
Surface Flux ◽  
Co2 Concentration ◽  
Early Morning ◽  
Nocturnal Boundary Layer ◽  
Maximum Height ◽  
Carbon Dioxide Concentrations ◽  
The Difference

Abstract. Measurements of carbon dioxide concentration, temperature and windspeed were made in the nocturnal boundary layer over a tropical forest near Manaus, Brazil using a tethered balloon system. The measurements were made up to a maximum height of 300 m on ten consecutive nights in November 1995. Simultaneous surface flux and in-canopy concentration measurements were made at the surface close to the site. The observation period included several different types of conditions. Generally strong windshear and relatively weak temperature gradients prevented the formation of a strong capping inversion to the nocturnal boundary layer. On some nights, however, the inversion was sufficiently strong that the CO2 concentration at 100 m above the surface exceeded 400 ppm. The concentration within the canopy was largely controlled by the presence of an inversion very close to the canopy surface. The temperature and wind profiles are contrasted with conditions in Randônia, Brazil, where the windshear was found to be weaker and higher carbon dioxide concentrations were observed in the early morning. The difference in carbon dioxide concentrations in the nocturnal boundary layer between dusk and dawn is used to estimate the regional nighttime flux of carbon dioxide. The value obtained generally exceeds the measured surface flux and sometimes exceeds the sum of the surface flux and the in-canopy storage made at the tower site. The reasons for the discrepancy are not clear; either one of the methods is in error or the regional carbon dioxide budget differs significantly from the local budget measured at the tower site.

scholarly journals Implementation of a boundary layer heat flux parameterization into the Regional Atmospheric Modeling System (RAMS)

2008 ◽  
Vol 8 (4) ◽  
pp. 14311-14346 ◽  
Author(s):  
E. L. McGrath-Spangler ◽  
A. S. Denning ◽  
K. D. Corbin ◽  
I. T. Baker
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Heat Flux ◽  
Lower Layer ◽  
Bowen Ratio ◽  
Surface Flux ◽  
Atmospheric Modeling ◽  
Surface Energy Budget ◽  
Stress Factors ◽  
Surface Boundary

Abstract. The response of atmospheric carbon dioxide to a given amount of surface flux is inversely proportional to the depth of the boundary layer. Overshooting thermals that entrain free tropospheric air down into the boundary layer modify the characteristics and depth of the lower layer through the insertion of energy and mass. This alters the surface energy budget by changing the Bowen ratio and thereby altering the vegetative response and the surface boundary conditions. Although overshooting thermals are important in the physical world, their effects are unresolved in most regional models. A parameterization to include the effects of boundary layer entrainment was introduced into a coupled ecosystem-atmosphere model (SiB-RAMS). The parameterization is based on a downward heat flux at the top of the boundary layer that is proportional to the heat flux at the surface. Results with the parameterization show that the boundary layer simulated is deeper, warmer, and drier than when the parameterization is turned off. These results alter the vegetative stress factors thereby changing the carbon flux from the surface. The combination of this and the deeper boundary layer change the concentration of carbon dioxide in the boundary layer.

scholarly journals Estimating the atmospheric boundary layer height over sloped, forested terrain from surface spectral analysis during BEARPEX

2010 ◽  
Vol 10 (11) ◽  
pp. 25759-25801 ◽  
Author(s):  
W. Choi ◽  
I. C. Faloona ◽  
M. McKay ◽  
A. H. Goldstein ◽  
B. Baker
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Sierra Nevada ◽  
Sonic Anemometer ◽  
Coniferous Forest ◽  
Power Spectra ◽  
Nocturnal Boundary Layer ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Stable Conditions

Abstract. In this study the atmospheric boundary layer (ABL) height (zi) over complex, forested terrain is estimated based on the power spectra and the integral length scale of horizontal winds obtained from a three-axis sonic anemometer during the BEARPEX (Biosphere Effects on Aerosol and Photochemistry) Experiment. The zi values estimated with this technique showed very good agreement with observations obtained from balloon tether sonde (2007) and rawinsonde (2009) measurements under unstable conditions (z/L < 0) at the coniferous forest in the California Sierra Nevada. The behavior of the nocturnal boundary layer height (h) and power spectra of lateral winds and temperature under stable conditions (z/L > 0) is also presented. The nocturnal boundary layer height is found to be fairly well predicted by a recent interpolation formula proposed by Zilitinkevich et al. (2007), although it was observed to only vary from 60–80 m during the experiment. Finally, significant directional wind shear was observed during both day and night with winds backing from the prevailing west-southwesterlies in the ABL (anabatic cross-valley circulation) to consistent southerlies in a layer ~1 km thick just above the ABL before veering to the prevailing westerlies further aloft. We show that this is consistent with the forcing of a thermal wind driven by the regional temperature gradient directed due east in the lower troposphere.

scholarly journals Net ecosystem CO<sub>2</sub> exchange measurements by the closed chamber method and the eddy covariance technique and their dependence on atmospheric conditions – a case study

2013 ◽  
Vol 6 (5) ◽  
pp. 8783-8805 ◽  
Author(s):  
M. Riederer ◽  
A. Serafimovich ◽  
T. Foken
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Net Ecosystem Exchange ◽  
Carbon Dioxide Flux ◽  
Atmospheric Conditions ◽  
Closed Chamber ◽  
Carbon Dioxide Fluxes ◽  
Chamber Method ◽  
Eddy Covariance Technique ◽  
Closed Chamber Method

Abstract. Carbon dioxide flux measurements in ecosystem sciences are mostly conducted by eddy covariance technique or the closed chamber method. Also some comparisons have been performed. But there is a lack of detailed assessment of present differences and uncertainties. To determine underlying processes, a ten-day, side-by-side measurement of the net ecosystem exchange with both techniques was evaluated with regard to various atmospheric conditions during the diurnal cycle. It was found that, depending on the particular atmospheric condition, the chamber carbon dioxide flux was either: (i) equal to the carbon dioxide flux measured by the reference method eddy covariance, by day with well developed atmospheric turbulence, (ii) higher, in the afternoon in times of oasis effect, (iii) lower, predominantly at night while large coherent structure fluxes or high wind velocities prevailed, or, (iv) showed less variation in the flux pattern, at night while stable stratification was present. Due to lower chamber carbon dioxide fluxes at night, when respiration forms the net ecosystem exchange, and higher chamber carbon dioxide fluxes in the afternoon, when the ecosystem is still a net carbon sink, there are two complementary aspects resulting in an overestimation of the ecosystem sink capacity by the chamber of 40% in this study.

scholarly journals Development of an Atmospheric Carbon Dioxide Standard Gas Saving System and Its Application to a Measurement at a Site in the West Siberian Forest

2010 ◽  
Vol 27 (5) ◽  
pp. 843-855 ◽  
Author(s):  
T. Watai ◽  
T. Machida ◽  
K. Shimoyama ◽  
O. Krasnov ◽  
M. Yamamoto ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Boundary Layer ◽  
Atmospheric Carbon Dioxide ◽  
Western Siberia ◽  
Atmospheric Stability ◽  
Co2 Concentration ◽  
Atmospheric Conditions ◽  
The West ◽  
A Site ◽  
Standard Gas

Abstract Observations of the atmospheric CO2 concentration from a 90-m tower in Berezorechka, western Siberia, that have taken place since October 2001 were used to characterize CO2 variations over a vast boreal forest area. A new CO2 standard gas saving system was developed that reduced the consumption of standard gases and kept the analysis precision to within 0.3 μmol mol−1. The CO2 day-to-day variation correlated well with atmospheric stability. The average amplitudes of the diurnal variation at 80 m were found to be about 17 and 1.5 μmol mol−1 in July and December 2003, respectively. Extremely high daytime CO2 concentrations of greater than 400 μmol mol−1 were occasionally observed during the winter, which were caused by anticyclonic atmospheric conditions lasting more than several days. Afternoon CO2 values observed at the 80-m height agreed to within 0.4 μmol mol−1 with aircraft CO2 measurements taken in the planetary boundary layer; disagreements were found for anticyclonic conditions in the winter. The afternoon CO2 values reached their maximum in mid-January and their minimum late in July, with the seasonal amplitude of 30.9 μmol mol−1. Compared to observations at background stations, this observation tower recorded a larger seasonal amplitude and earlier occurrence of the seasonal minimum.

scholarly journals The Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer Project (ISOBAR) —Unique fine-scale observations under stable and very stable conditions

2020 ◽  
pp. 1-64
Author(s):  
Stephan T. Kral ◽  
Joachim Reuder ◽  
Timo Vihma ◽  
Irene Suomi ◽  
Kristine Flacké Haualand ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
The Arctic ◽  
Fine Scale ◽  
Stable Boundary ◽  
Innovative Strategies ◽  
Aircraft Systems ◽  
Stable Conditions

Capsule summaryCombining ground-based micrometeorological instrumentation with boundary layer remote sensing and unmanned aircraft systems for high-resolution observations on the stable boundary layer over sea ice and corresponding modelling experiments.

scholarly journals Evening transitions of the atmospheric boundary layer: characterization, case studies and WRF simulations

2012 ◽  
Vol 8 (1) ◽  
pp. 39-44 ◽  
Author(s):  
M. Sastre ◽  
C. Yagüe ◽  
C. Román-Cascón ◽  
G. Maqueda ◽  
F. Salamanca ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Case Studies ◽  
Mesoscale Model ◽  
Atmospheric Stability ◽  
Nocturnal Boundary Layer ◽  
Weather Research And Forecasting ◽  
Atmospheric Conditions ◽  
Different Types ◽  
Turbulence Parameters

Abstract. Micrometeorological observations from two months (July–August 2009) at the CIBA site (Northern Spanish plateau) have been used to evaluate the evolution of atmospheric stability and turbulence parameters along the evening transition to a Nocturnal Boundary Layer. Turbulent Kinetic Energy thresholds have been established to distinguish between diverse case studies. Three different types of transitions are found, whose distinctive characteristics are shown. Simulations with the Weather Research and Forecasting-Advanced Research WRF (WRF-ARW) mesoscale model of selected transitions, using three different PBL parameterizations, have been carried out for comparison with observed data. Depending on the atmospheric conditions, different PBL schemes appear to be advantageous over others in forecasting the transitions.

scholarly journals Net ecosystem CO<sub>2</sub> exchange measurements by the closed chamber method and the eddy covariance technique and their dependence on atmospheric conditions

2014 ◽  
Vol 7 (4) ◽  
pp. 1057-1064 ◽  
Author(s):  
M. Riederer ◽  
A. Serafimovich ◽  
T. Foken
Keyword(s):  
Carbon Dioxide ◽  
Eddy Covariance ◽  
Net Ecosystem Exchange ◽  
Carbon Dioxide Flux ◽  
Atmospheric Conditions ◽  
Closed Chamber ◽  
Carbon Dioxide Fluxes ◽  
Chamber Method ◽  
Eddy Covariance Technique ◽  
Closed Chamber Method

Abstract. Carbon dioxide flux measurements in ecosystem sciences are mostly conducted by eddy covariance technique or the closed chamber method. But there is a lack of detailed comparisons that assess present differences and uncertainties. To determine underlying processes, a 10-day, side-by-side measurement of the net ecosystem exchange with both techniques was evaluated with regard to various atmospheric conditions during the diurnal cycle. It was found that, depending on the particular atmospheric condition, the chamber carbon dioxide flux was either (i) equal to the carbon dioxide flux measured by the reference method eddy covariance, by day with well-developed atmospheric turbulence; (ii) higher, in the afternoon in times of oasis effect; (iii) lower, predominantly at night while large coherent structure fluxes or high wind velocities prevailed; or (iv) showed less variation in the flux pattern, at night while stable stratification was present. At night – when respiration forms the net ecosystem exchange – lower chamber carbon dioxide fluxes were found. In the afternoon – when the ecosystem is still a net carbon sink – the carbon dioxide fluxes measured by the chamber prevailed. These two complementary aspects resulted in an overestimation of the ecosystem sink capacity by the chamber of 40% in this study.

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